MAterial type bands constants models coeffs
The MATERIAL line associates physical parameters with the materials in the mesh. Many of the parameters are default for standard materials. These are included in a library of include files in the PADRE src directory. The current value of MATERIAL parameters can be examined using the PRINT line or "print" on the MODELS line. Below, the asterisk "*" stands for either "N" or "P" so that separate coefficients for each can be specified for electrons and holes respectively. Parameters marked with a dagger (++) can have separate values in n-type and p-type material.
NAme = character DEFault = character ALloy = character COmposition = real NO.charge = logical N.Type = logical P.Type = logical
NAME is the name of the material to be accessed or defined. DEFAULT is the name of a recognized (library or predefined) material which will be used to default all parameters; alternatively ALLOY is the name of an alloy definition from which the coefficients for this material can be interpolated using the compositional fraction 0 <= COMPOSITION <= 1. For those materials which PADRE recognizes, standard library definitions will be used. NO.CHARGE ignores space charge in this region when solving the Poisson equation which can be useful for conductors.
N.TYPE and P.TYPE permit separate coefficient values for a large number of the available material parameters (marked with ++ below). If any other parameters are set on the same MATERIAL input line, they are valid for both n-type and p.type material (a warning is given). When separate values are selected, these are appropriately marked in material coefficient printouts by the addition of an "N" or "P" character to the associated material index. By default, both N.TYPE and P.TYPE are turned on. If the user puts one explicityly on the input line, the other then defaults to false.
bands
EG300 = real Energy gap at 300K (eV) EGAlpha = real Alpha EGBeta = real Beta AFfinity = real Electron affinity (eV) DECDEV = real DELTA Ec / DELTA Ev DECDEG = real DELTA Ec / DELTA Eg EC.off = real DELTA Ec (eV) Refoff = character Offtemp = real (default is 300K)
The above parameters specify the energy band configurations. Default band offsets are computed using electron affinities. These can be overridden using one of DECDEV, EC.OFF or DECDEG which are referenced to the material named REFOFF; the offset is given at the temperature OFFTEMP and converted to the ambient temperature used in the simulation. The resulting band offsets are printed with all other material parameters.
constants
PErmittivity = real Dielectric permittivity (F/cm) Qf = real Fixed bulk charge density (/cm**3) NC300 = real Conduction band density at 300K (/cm**3) NV300 = real Valence band density at 300K (/cm**3) GCb = real Conduction-band degeneracy factor GVb = real Valence-band degeneracy factor EDb = real Donor energy level (eV) EAb = real Acceptor energy level (eV) W2dgas = real Width of 2D gas (mm) ARICHN = real Richardson constant for electrons ARICHP = real Richardson constant for holes VSAT* = real Saturation velocity - 300K (cm/s) TAUW* = real Intrinsic low field energy relaxation times (s) MU* ++ = real Intrinsic mobility - 300K (cm**2/s) TAU*0 ++ = vector Intrinsic minority carrier lifetimes (s) TAUR0 ++ = real Intrinsic radiative lifetime (s) AUG* ++ = real Auger coefficient (Cn) (cm**6/s) C.helm = real Helmholtz coefficient (default is 0.0)
These are basic material constants as defined above. W2DGAS is used only in conjunction with 2dgas statistics (see the MODEL line). The energy relaxation times are only used if no relaxation model (W*.MODEL below) is given; carrier effective masses are currently unused. C.HELM is the coefficient in front of a term, linear in potential, added to the Poisson equation for this region; it is useful in performing contact resiatance studies (see Loh, et.al. EDL, 1985).
models
I*.Model = character Ionized impurity scattering (CONMOB) E*.Model = character Velocity saturation model (FLDMOB) G*.Model = character Gate-field mobility model (GATMOB) C*.Model = character Carrier-carrier scattering model (CCMOB) D*.Model = character Diffusivity-field model (FLDDIF) W*.Model = character Energy relaxation model (FLDMOB) S*.Model = character Energy flux coefficient model BGN*.model = character Band-gap narrowing model
These are material-dependent model types; the first six correspond to mobility models defined on the MODELS line. W*.MODEL and S*.MODEL are only relevant if carrier temperatures are solved for. Possible choices are:
I*.Model = table, analytic, klaasen E*.Model = caughey, barnes, limit, scharfetter, alley, hansch G*.Model = pinto, yamaguchi, sun, caughey, schwarz, sgs, lentz, mujtaba C*.Model = dorkel, klaasen D*.Model = mccoll W*.Model = none, baccarani, lincut, hypcut, npar, general S*.Model = constant, mc BGN*.Model = slotboom, cak-sige
Descriptions of these models are available in another document. Coefficients for each model can be adjusted below.
coeffs
*.Bgn ++ = vector BGN coefficients L*.Mu ++ = vector Lattice mobility coeffs II*.Mu ++ = vector Ionized impurity scattering coeffs NIN*.Mu ++ = vector Neutral impurity scattering coeffs CC*.Mu = vector Carrier-carrier scattering coeffs E*.Mu = vector Nonlinear drift velocity (vs. field) coeffs G*.Mu = vector Gate-field scattering coeffs D*.Mu = vector Diffusivity vs. field coeffs W*.Mu = vector Carrier temperature mobility coeffs W*.Kappa = vector Thermal conductivity proportionality coeffs NTAU* ++ = real min-carr. lifetime conc. param (/cm**3) B0dir ++ = real Radiative-lifetime coeff (cm**3/s) NTAUR ++ = real Radiative-lifetime conc. param (/cm**3) GEn.con ++ = real Generation constant (eh pairs/cm**3/rad) TRap.type = character trap types ETrap = vector trap energy levels = Et - Ei (eV) NTRap = vector trap densities (/cm**3) E*.Ion = vector Impact-ionization field threshs (V/cm) A*.Ion = vector Impact-ionization rate (/cm) B*.Ion = vector Impact-ionization assym field (V/cm) W*.Etpar = vector New energy transport model coefficients C.tunnel = vector Band-to-band tunneling coefficients Laser ++ = vector Stimulated-emission coeffs
These are coefficients for various models, e.g. band-gap narrowing, mobility, lifetime, impact ionization and energy relaxation. The scalar parameters are relatively self-explanatory; see the technical reference manual for more details.
The vector parameters for traps allow for multiple trap levels with different minority lifetimes and densities (the densities are only required for deep-level traps). The type of the traps (standard SRH or deep-level acceptor/donor) is determined by the string TRAP.TYPE, where each character refers to its corresponding element in the vector parameters; possible types are "n" (donor), "p" (acceptor) and "0" (SRH) with a default of "0" for all unspecified. The vector parameters for impact ionization permit multiple field regimes.
The remaining vector quantities define models which require several parameters. See primary documentation for detailed descriptions of model forms and coefficient definitions.
Types of Diffusion Noise Models
ns.model = character
ns.model specifies the types of diffusion model is desired. ns.model=diffmu specifies that differential mobility model is used to compute microscopic noise sources, ns.model=incmu specifies that incremental mobility model is used [default], ns.model=userdiff requires that the user supply the field-dependent diffusivity model, and ns.mode=userbeta requires that the user supply the field dependent beta (ratio of diffusivity and mobility) model. These user defined files are to be included in userdiff.f.
Specify two trap levels in all silicon regions, one at midgap and the second 0.2eV above, with lifetimes of 1ms and 500ns respectively; the first trap involves standard SRH recombination whereas the second is a deep-level donor trap with a density of 1.0e15/cm**3. Also set the hole ionization coeffs to those suggested by van Overstraeten.
MATERIAL NAME=silicon TAUN0=1e-6,5e-7 TAUP0=1e-6,5e-7 ETRAP=0,0.2 + N.TRAP=0,1e15 TRAP.TYP=0n + EP.ION=1.75e5,4e5 AP.ION=1.58eE6,6.71E5 + BP.ION=2.036E6,1.693E6
Define a material called "likesi" to be silicon with some changes to the gate-field mobility and analytic ionized impurity scattering models for electrons. Also, include the differential mobility model for noise calculations.
MATERIAL NAME=likesi DEF=silicon + GN.MOD=sgs GN.MU=4.75e7,1.74e5,0.125,5.84e14 + IN.MOD=analyt IIN.MU=55.24,1.072e17,0.733,-3.8 + NS.MODEL=diffmu
Define a material called "sige.3" using a previously defined alloy called "sige"; the compositional fraction is 0.3, hence the material is interpolated as Si(0.7)Ge(0.3) (see the ALLOY line documentation). Override the default (interpolated) energy gap, band offset and bulk mobilities and lifetimes.
ALLOY NAME=sige X1ALLOY=0 M1ALLOY=silicon + X2ALLOY=1 M2ALLOY=germanium MATERIAL NAME=sige.3 DEF=sige COMP=0.3 + EG300=0.830 DECDEV=0.087 REFOFF=silicon + MUN0=242 MUP0=186 TAUN0=50e-6 TAUP0=50e-6
Set separate SRH lifetimes for n-type and p-type material called "polysi". Because the EG300 parameter cannnot have separate n.type and p.type values, it is defined as 1.05eV for both types, eventhough the value is given on a line with an "n.type" modifier.
MATERIAL NAME=polysi EG300=1.05 TAUN0=6e-6 TAUP0=3e-6 N.TYPE MATERIAL NAME=polysi TAUN0=4e-6 TAUP0=2e-6 P.TYPE